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150 PATHOLOGY OF THE HABD TISSUES OF THE TEETH.
tice. But the relief of suffering is an ever-present duty and the
search for this very desirable thing should continue.
THERMAL SENSITIVENESS.
The consideration of thermal sensitiveness more properly
belongs to special pathology and therapeutics, but it is so closely
interwoven with the management of cases in filling teeth that it
is necessary to consider it here. Thermal sensitiveness is a
peculiar painful sensation in the teeth caused by changes of tem-
perature. This may be illustrated by taking ice-water in the
mouth and letting it come suddenly in full contact with the teeth.
This causes sharp pain, lasting only a moment, the character of
which is well known from personal experience by most persons.
This is peculiar to the teeth, no other tissue in the body, no other
organ, showing a like resistance to thermal changes. This is
normal. Under certain conditions, this becomes a hypersensi-
tiveness to thermal changes it becomes augmented and becomes
;
a pathological condition. The actual condition in this case is a
hyperemia of the pulp. There is an injury to the walls of the
veins, particularly, and, to some extent, to the arterioles of the
pulp, by which they become very much dilated; indeed, each
manifestation of pain in this way is brought about by a dilation
of the blood vessels of the pulp and forcing of an extra quantity
of blood into them. When the walls of the vessels become so
injured that they are more readily expanded than normal, this
becomes a pathological condition and every slight change of
temperature produces a paroxysm of pain. This is called ther-
mal sensitiveness. It is entirely separate and distinct from sen-
sitiveness of dentin. TVe may have sensitive dentin existing and
continuing for a long time without any particular thermal sen-
sitiveness, or we may have thermal sensitiveness without abnor-
mal sensitiveness of the dentin, or we may have the two existing
together. They are distinct conditions.
Thermal sensitiveness may be aroused in many different
ways. It is sometimes caused in the incisor teeth by the heat
of a cigar in smoking; it may be caused suddenly by an extraor-
dinary exposure to cold, as ice-wateE; it may be caused sud-
denly by exposure to hot drinks, and the dentist may develop it
suddenly by the heat of a disk in finishing a filling, or the heat
of a bur in excavating in any tooth that has a living pulp.
Often thermal sensitiveness is aroused during the progress of
decay, especially when the decay has reached the neighborhood
of the pulp, sometimes when the decay has not nearly reached